1. Field of the Invention
This invention relates to an image processing system. In particular, this invention relates to an apparatus and a method for processing and displaying an image of the surrounding of a vehicle to a driver.
2. Related Art
Modern vehicles provide sophisticated functionalities to its drivers. Recently, the development of systems is being discussed in which a driver is provided with an image of the surrounding of the vehicle on a small display in the cockpit of the vehicle. This is, for example, especially helpful in the case when the position of the driver in the vehicle does not allow the driver to visually gather all relevant information. Driving into a parking spot could be such a situation in which positioning a camera at the backside of the vehicle may be beneficial. For example, providing an image of the vehicle surroundings from a camera to a display in the cockpit could strongly assist the driver in quickly reaching a parking position. Another example could be capturing an image of a road before the vehicle when sight is obscured by fog or supervising the rear part of the road for approaching vehicles. Before displaying such an image, the picture data can then be processed to improve recognition of objects in the fog. Displaying such picture at the display in the cockpit of the vehicle would then provide the advantage of earlier recognizing obstacles on the road such that, for example, an adaption of the speed of the vehicle can be performed in time. However, processing and/or displaying such a picture normally requires an analog-to-digital-conversion or even a direct digital capture of the image. Furthermore, a transfer and the display of such an image has a high latency since conventional systems work on a whole video image approach. This means that only complete video images are captured consecutively by a sensor and are processed or transferred as a complete image.
Such a conventional approach of processing whole images can be seen in FIG. 1. FIG. 1 is a schematic scheme illustrating a conventional image processing approach for processing different images at different processing or generation stages. At the ordinate of FIG. 1, different pipeline stages, for example, the image generation (stage 1), an image transfer (stage 2), image processing (stage 3), image display (stage n), etc. are depicted. At the abscissa of FIG. 1, a time duration is depicted. As can be seen from FIG. 1, the first image (Image 1) is generated at stage 1, which can be concluded from the Image 1 being located at a first position 100. However, generating Image 1 in the first position 100 takes a time tp which can be concluded from the abscissa of FIG. 1. Subsequently, Image 1 is transferred to stage 2, which then processes Image 1 at a later time instant (see position 202 in FIG. 1). Stage 1 generates a new image, now denoted as Image 2 (see position 204 in FIG. 1). When stage 2 has completed processing Image 1, Image 1 is transferred to stage 3 and Image 2 his transferred from stage 1 to stage 2. Furthermore, a new image, namely Image 3, is generated in stage 1. In this case, the processing (i.e., respectively generating) of an image includes several stages and the latency in which the image is processed completely can be calculated by the formula ttotal=tp*n. This total latency ttotal is depicted on the abscissa of FIG. 1.
More precisely, given a capture frequency f, it takes a time of 1/f to get a complete image. Even if the steps of processing or displaying can be performed much faster, it is not possible to increase the image rate as the sensor only provides images in an image rate of 1/f. Typical image rates of conventional sensors (i.e. cameras) provide images with an image rate f=25/s, which results in an image latency of 40 ms. When latency for displaying or processing is also considered, the latency of conventional systems easily rises above 80 ms. In contrast, it has to be mentioned that the human visual system has a much lower latency such that displaying an image on a display in the cockpit with a latency above 80 ms will result in an irritation of the driver of the vehicle. This, in turn, reduces the safety of the vehicle as the driver's attention is drawn off the traffic situation.
Therefore, a need exists for providing an improved way for processing an image in a vehicle, in particular, an improved system for processing an image of the surrounding of a vehicle.